It has become clear that Jimmy Fallon is going to become the host of The Tonight Show, but sources say an internal debate among key players is underway regarding the timing.

According to these sources, some top executives at NBCUniversal are leaning toward a February launch to take advantage of the promotional platform of the 2014 Winter Olympics in Sochi, Russia. Others, including Late Night executive producer Lorne Michaels, are said to have concerns about rushing the transition.

Moving more quickly not only would provide a high-profile launch for Fallon but effectively would keep Tonight Show host Jay Leno from moving to a rival network until his contract expires in September 2014.

As The Hollywood Reporter first reported, an announcement is expected to be made at the May upfront presentation to advertisers. With Fallon expected to launch as host in September 2014, Tonight will move from Los Angeles to New York, according to sources.

In a Fallon cover story for the April issue of GQ, Michaels confirmed that a shift is underway: "I'm not allowed to say it -- yet. But I think there's an inevitability to it. He's the closest to [Johnny] Carson that I've seen of this generation."

NBC Entertainment chairman Bob Greenblatt and his late night and alternative chief Paul Telegdy are said to be actively looking for a Fallon replacement at 12:35 a.m. One possibility is another Michaels protege, Seth Meyers of Saturday Night Live.

The latest news comes as Leno continues to take jabs at NBC execs including Greenblatt, who reportedly sent Leno an email to back-off on the ridicule. On Monday’s show, Leno quipped during his monologue: "You know the whole legend of St. Patrick, right? St. Patrick drove all the snakes out of Ireland -- and then they came to the United States and became NBC executives. It's a fascinating story."

On Tuesday, he made another joke: "Did you hear about this? A 28-year-old woman from Serbia has a rare brain condition where she sees everything upside down. The good news? She's now been given a job at the White House as President Obama's economic adviser. Isn't that crazy? It's unbelievable. She sees everything upside down. In fact, she thinks NBC is at the top of the ratings."

The exchange between Greenblatt and Leno is said to have occurred before THR reported March 1 that NBC was discussing an exit plan for Leno. NBC has denied the report.

NBC confirms that it is upgrading Fallon's studio in New York as part of a larger renovation of the building but declines further comment.